Brussels sprouts are a cultivar group of Brassica oleracea grown for the dense edible buds that form in leaf axils along the main stem. Each plant produces a stalk bearing 20–40 sprouts that mature progressively from the base upward. The crop requires 80–110 days to maturity and tolerates hard frost, making it one of the most cold-tolerant vegetables grown in kitchen gardens.
Frost converts starches to sugars in the sprouts, noticeably reducing bitterness and improving flavor. A fall crop — started indoors in early summer and transplanted to mature after the first fall frost — generally outperforms a spring crop in most temperate zones. Soil should be firm and fertile; loose or sandy soil produces open, leafy sprouts rather than tight buds. Consistent nitrogen and moisture are critical throughout the growing season. Maintaining pH between 6.5 and 7.5 significantly reduces clubroot infection. Removing lower yellowing leaves as sprouts develop improves airflow and reduces disease pressure.
Brussels sprouts are high in vitamin C, vitamin K, folate, and glucosinolates. Glucosinolates are sulfur-containing compounds that have been extensively studied in relation to cancer prevention; they also produce the sulfurous bitterness some people find unpleasant. Steaming retains more glucosinolates and vitamin C than boiling.
Clubroot
Swollen, distorted roots; wilting in midday heat; stunted growth and yellowing foliage. Plants recover poorly even with watering.
Remove and destroy infected plants with roots. Raise soil pH toward 7.2 with lime. Improve drainage and rotate out of brassicas for several years.
Black Rot
Yellow, V-shaped lesions spreading inward from leaf margins, with blackened veins. Severe cases cause wilting and leaf drop.
Remove and destroy infected plants. Use disease-free seed, rotate brassicas on a 3-year cycle, avoid overhead watering, and keep tools and beds clean.
Downy mildew
Yellowing on top of leaves with grey-purple fuzz underneath. Spreads rapidly in humid conditions.
Remove affected leaves. Improve air circulation. Avoid overhead watering. Copper spray as preventive.
White Rust
Raised white to cream-colored pustules on leaf undersides, with yellow blotches on upper surfaces. Infected tissue may swell or distort.
Remove and destroy infected leaves. Improve air circulation and avoid overhead watering. Rotate brassicas and avoid planting in previously infected soil.
Alternaria blight
Brown circular spots with yellow halos on leaves; spreads rapidly in wet weather.
Remove affected leaves immediately. Water at the base only. A copper-based fungicide can help if caught early.
Black Leg
Stem base blackens and rots at or just below the soil line, causing plants to yellow, wilt, and collapse. Infected tubers develop a slimy, foul-smelling internal rot. Disease spreads through contaminated seed pieces and is worsened by waterlogged soils.
Plant only certified seed potatoes and ensure all cut surfaces are fully cured before planting. Avoid planting in poorly drained or compacted soils. Remove and destroy infected plants and any associated tubers. No curative chemical treatment exists; prevention through clean planting material, proper drainage, and crop rotation of 3 or more years is the primary strategy.
Damping Off
Seedlings collapse at the soil line with thin, water-soaked stems; seeds may fail to emerge or rot before sprouting.
Sow in well-draining mix, avoid overwatering, and ensure good airflow. Remove affected seedlings and let the surface dry between waterings.
Brassica Ring Spot
Circular tan to brown leaf spots with dark purple or black borders; spots enlarge and may coalesce under wet conditions. In heavy infections, surface lesions develop on the sprouts themselves, reducing quality.
Remove and destroy infected leaves promptly. Avoid overhead irrigation. Apply copper-based fungicide preventively during cool, wet weather. Rotate brassicas on a minimum three-year cycle with non-host crops.
Cabbage Worm
Pieris rapae →Ragged holes in leaves and green velvety caterpillars on undersides; dark green frass collects in leaf crevices and head.
Handpick caterpillars and eggs. Apply Bacillus thuringiensis (Bt) weekly during egg-laying. Use floating row cover to exclude white cabbage moths.
Cabbage Looper
Trichoplusia ni →Ragged, irregular holes in outer and wrapper leaves caused by pale green caterpillars that arch their bodies in a looping motion when moving. Heavy populations consume leaf tissue down to the midrib and bore into forming heads.
Apply Bacillus thuringiensis var. kurstaki (Bt) at the first sign of feeding, targeting larvae while they are small. Reapply every 5–7 days during wet weather. Use floating row cover to exclude egg-laying adults. Hand-pick caterpillars on small plantings. Parasitic wasps are effective natural controls; avoid broad-spectrum insecticides that kill them.
Cabbage Root Maggot
Delia radicum →Seedlings wilt suddenly despite adequate moisture. Roots show surface scarring and interior tunneling from small, creamy-white larvae feeding at and just below the soil line. Young transplants may collapse and die; older plants produce stunted, loose heads.
Apply floating row cover immediately after transplanting to prevent adult flies from laying eggs at the soil line. Drench soil with beneficial nematodes (Steinernema feltiae) before planting. Remove and dispose of infested plants and surrounding soil. Rotate all brassicas to a new bed each season.
Aphids
Aphididae →Clusters of small soft insects on new growth and flower buds.
Knock off with a strong jet of water. Ladybirds and lacewings are natural predators. Insecticidal soap as last resort.
Flea Beetle
Alticini →Small round shot-holes scattered across leaves; tiny dark beetles that jump when disturbed. Heavy feeding stunts young plants.
Use floating row covers on seedlings. Remove crop debris and weeds that harbor beetles. Apply kaolin clay or spinosad if damage is severe.